[HIVE-11174] Hive does not treat floating point signed zeros as equal (-0.0 should equal 0.0 according to IEEE floating point spec)

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.2.0
• Fix Version/s: 2.0.0
• Component/s: Query Processor
• Assignee: Sergio Peña
• Reporter: Lenni Kuff
• Created: 02/Jul/15 19:43
• Updated: 02/Sep/20 21:33
• Resolved: 15/Jul/15 14:48

Description

Hive does not treat floating point signed zeros as equal (-0.0 should equal 0.0). This is because Hive uses Double.compareTo(), which states (http://docs.oracle.com/javase/7/docs/api/java/lang/Double.html#compareTo(java.lang.Double):

0.0d is considered by this method to be greater than -0.0d

The IEEE 754 floating point spec specifies that signed -0.0 and 0.0 should be treated as equal. From the Wikipedia article (https://en.wikipedia.org/wiki/Signed_zero#Comparisons):

negative zero and positive zero should compare as equal with the usual (numerical) comparison operators

Java's compareTo method is implemented to allow for ordering of object instances (in a hash table or similar), but Hive should abide by the IEEE spec.

How to reproduce:

select 1 where 0.0=-0.0;
Returns no results.

select 1 where -0.0<0.0;
Returns 1

Issue Links

• is related to: SPARK-32764 compare of -0.0 < 0.0 return true